February 21, 2006
From: ProMED-mail<promed@promedmail.org>
In this update:
-
Asian soybean rust (ASR) on kudzu, Dade County FL (13
Feb 2006)
-
Significance of kudzu as alternate host for ASR
-
New finds of ASR on kudzu in Georgia & Florida (13 Feb
2006)
-
Rust spores found in rain
-
National Map Commentary (updated: 17 Feb 2006)
-
Ohio to
use sentinel plots in 2006
[1] Asian soybean rust (ASR) on kudzu, Dade County FL (13 Feb
2006)
Date: 13 Feb 2006
From: ProMED-mail <promed@promedmail.org>
Source: Stopsoybeanrust.com [edited]
<http://www.stopsoybeanrust.com/viewStory.asp?StoryID=684>
ALERT: Florida finds ASR in same Dade County kudzu as last year
[2005]
The kudzu site in Dade County, Florida that was confirmed with
ASR on 29 Apr 2005 (last year) was found to have ASR sporulating
on its still-green leaves last week [2nd week February 2006].
In today's [13 Feb 2006] Florida state commentary
<http://www.sbrusa.net>, University of Florida plant pathologist
James Marois reported: "In another pass through Florida last
week, the positive 2005 kudzu site in Dade County was found
again to be positive. Leaves were green and the fungus was
sporulating. We are seeing the coldest weather of the season
this week. In Quincy, there was a lot of frost this morning and
ice on the edge of shallow waters."
Marois recommended consulting the Florida Automated Weather
Network Web site for specific weather information across
Florida.
The 29 Apr 2005 ASR find in Dade County (home to Miami in
southeast Florida) was the 4th of the season for the state. It
was also the 1st 2005 Florida find south of the nation's 1st
confirmed ASR of the year in Pasco County, Florida, on 23 Feb
2005.
Florida had one county positive for ASR post-season in 2004,
Gadsden County. ASR was confirmed there in a university test
plot in Quincy on 17 Nov 2004. In 2005, Gadsden County was
confirmed to have ASR on
17 Jul 2005, and this year [2006] was one of 9 Florida counties
with ASR announced on 17 Jan 2006.
Florida is now reporting 11 counties positive for ASR in 2006,
bringing the U.S. total to 14 positive counties.
--
ProMED-mail
<promed@promedmail.org>
[2] Significance of kudzu as alternate host for ASR
Date: 13 Feb 2006
From: ProMED-mail <promed@promedmail.org>
Source:
Dtnsoybeanrustcenter.com [edited] <http://www.dtnsoybeanrustcenter.com/index.cfm?show=10&mid=65&pid=10>
Rust-Kudzu Relation Examined
Kudzu is an alternate host for ASR, but how much it contributes
to the rust threat in the U.S. is still being investigated.
Kudzu, one of 95 known hosts for Asian soybean rust, is right at
home in the south. The plant grows almost too well. Vines can
grow more than a foot a day during summer months, climbing
trees, power poles and anything else they contact. Kudzu plants
will survive the winters in the south, but freezing temperatures
will kill off any green leaves.
If the plants survive, ASR will overwinter on kudzu.
Kudzu was introduced to the United States in 1876 at the
Centennial Exposition in Philadelphia, Pennsylvania. During the
Great Depression of the 1930s, the Soil Conservation Service
promoted kudzu for erosion control. Hundreds of young men were
given work planting kudzu through the Civilian Conservation
Corps.
How it will affect the spread of ASR is still an uncertainty.
The plant is a very good host in Asia and South America but less
of an ideal host in the U.S. Tests on spore production of ASR on
kudzu has been inconsistent, which means it's not as good a host
here as elsewhere.
Kudzu growing along roadsides and in ditch banks in Brazil are
infected with ASR but show no apparent loss of plant vigor,
meaning the disease does not defoliate and kill the plant as it
does soybeans.
Morris Bonde, a research plant pathologist with the USDA at Fort
Detrick, Maryland said many hosts exist for ASR in the U.S.
"The ASR pathogen has a large host range, which is very rare for
rust pathogens. It infects at least 95 other species," he said.
In the U.S., we are concerned about clovers, cowpeas, green
beans, lima beans and kudzu, Bonde said. Clovers, alfalfa,
cowpeas and Lima beans do not sporulate [the fungus], so are of
little risk. Green beans and green peas are fairly susceptible
because they sporulate.
"Lupines are very susceptible, and there are over 150 individual
species that are susceptible," he said. "Kudzu is very
susceptible, has high sporulation, but the plant can tolerate
the disease."
Soybeans are the most susceptible species in the U.S. with high
sporulation and, if infected, quickly defoliate and die.
If a significant portion of kudzu is susceptible in the U.S.,
its importance to potential ASR epidemics cannot be
underestimated. The questions that remain unanswered are how
susceptible the kudzu is and do biotypes sporulate differently.
If so, will some provide a greater risk of inoculum production
than others?
The ASR pathogen can survive in Florida and Texas on kudzu in
areas that do not freeze. In years such as 2004-2005, in winter,
the kudzu froze back all the way down to the Gulf Coast. This
year [2006], some kudzu survived in protected areas, and ASR
will overwinter in areas that we did not expect, Bonde said.
"The earlier the disease gets into soybean growing areas, the
earlier the inoculum builds up and the greater the risk of
damage," he said.
Fortunately, what is in U.S. growers' favor is that rust does
not overwinter very well in the U.S. If it does survive and
survives over a greater number of sites along the Gulf Coast, we
could see an epidemic, Bonde said.
"Most people feel that the disease will do damage in some years
but not in others," he said, "and it may never reach the levels
of Brazil. In the U.S., kudzu is quite susceptible and is easily
infected in nature. However, we do not know much about its
sporulation ability. Observations in the U.S. show it becomes
infected easily, but does not get die or defoliate like
soybeans."
Some biotypes are susceptible, and others are not very
susceptible, Bonde said.
"In the U.S., kudzu is not nearly as susceptible as soybeans,
and the amount of infection is low enough that it does not knock
it back like it does soybeans," he said.
Perhaps kudzu grows so fast making it appear less susceptible,
so it does not get knocked back like soybeans, Bonde said.
Bonde and his colleagues at USDA are screening 50 biotypes of
kudzu they received from Mississippi. At Fort Detrick, USDA
maintains its containment greenhouse where they can test
pathogens without risk of them escaping into the environment.
It's in this facility Bonde plans to establish the kudzu
biotypes, inoculate them with the pathogen and test their
reaction to ASR and their ability to sporulate.
"It seems that we have some biotypes of kudzu that are
vulnerable," he said.
Response to ASR by the kudzu species is highly sporadic. Some
are easily infected and others not, and some sporulate heavily
and can be a major source of inoculum, while others will not.
Bonde said he doesn't yet know why the kudzu plant doesn't die
or totally defoliate as do soybeans. But reactions differ to the
disease, depending on the isolates.
"Different isolates of the pathogen react differently on
different kudzu plants. We are going to screen the different
biotypes with different isolates," he said.
The goal is to find out whether the most common biotypes of
kudzu in the U.S. either do not develop the disease or do not
heavily sporulate. That could be a good sign, because it would
mean populations of kudzu native to the U.S. would not be a
major source of inoculum, but only an overwintering green bridge
host.
[Byline: Dan Davidson <daniel.davidson@dtn.com>]
--
ProMED-mail
<promed@promedmail.org>
[3] New finds of ASR on Kudzu in Georgia and Florida (13 Feb
2006)
Date: 13 Feb 2006
From: ProMED-mail <promed@promedmail.org>
Source: Dtnsoybeanrustcenter.com [edited]
<http://www.dtnsoybeanrustcenter.com/index.cfm?show=10&mid=65&pid=8>
Culvert Protects Georgia Soybean Rust; Florida Finds 11th
Rust Case
Scouts found an ASR case on Friday [10 Feb 2006] in Thomas
County, Georgia on kudzu growing in a concrete culvert. Thomas
County, which is located along the Florida border, did not have
any positive ASR finds in 2005.
The site was scouted on 30 Jan 2006 with negative results, but
this time around, pustules and spores were found on the plant,
according to USDA's ASR Information Site. Both older and newer
green leaves were infected.
Scientists believe the culvert served as a "heat island,"
protecting the kudzu from low temperatures. Temperatures at the
site dropped to 30 F on 9 Feb 2006 and to 29 F on 10 Feb 2006.
"There was no sign of frost injury," USDA said. "Young, greening
kudzu tissue found on 30 Jan 2006 was frozen, foliage gone, but
vines had survived."
Friday's [10 Feb 2006] find boosts Georgia's rust case total to
2.
Florida found rust in Dade County on Monday [13 Feb 2006],
bringing its 2006 case total to 11. Alabama has one confirmed
case.
"It is unknown whether ASR is distributed more widely in the
southern U.S. in early February 2006 than it was one year ago,"
USDA said.
"There has been more extensive scouting this winter; all the
Florida kudzu locations that were positive for ASR in 2005 have
been scouted in January/February 2006 as well as many of the
kudzu sites where no ASR was found last year."
--
ProMED-mail
<promed@promedmail.org>
[4] Rust Spores Found in
Rain
Date: 13 Feb 2006
From: ProMED-mail <promed@promedmail.org>
Source: Dtnsoybeanrustcenter.com [edited]
<http://www.dtnsoybeanrustcenter.com/index.cfm?show=10&mid=65&pid=9>
More rust spores were found in rainwater in 2005 than
expected
One of the most interesting findings that came out late last
fall [2005] was that scientifically confirmed rust spores were
deposited by rainfall across much of the Corn Belt.
Les Szabo, a research geneticist at USDA's Cereal Disease
Laboratory
(CDL) at the University of Minnesota, was involved in a study in
2005, when they collected rainwater samples from a series of
collectors across the Corn Belt over the course of the summer
and fall, filtered out the particulate matter and then, using
molecular techniques, confirmed the presence of spores of ASR in
the rainwater.
But the test does not measure the viability of the spores or
their ability to germinate and infect leaves.
For many years, USDA has tracked the movement of wheat rust
spores northward. Scientists have found spores of wheat rust as
far north as the Dakotas as early as May, which indicates spores
can move long distances early in the year. Using this same
detection system, scientists said they could follow the movement
of ASR spores and detect them earlier than they thought
possible. But 1st, they needed the molecular tools to confirm
the identity of ASR spores.
"The risk of ASR raised the question of using the NADP (National
Atmospheric Deposition Program) wet deposition collection sites
to monitor rust spore movement," Szabo said.
The NAPD maintains a series of 250 rainwater collectors across
the US that were set up in the 1970s to monitor air pollution.
"NADP analyzes filtered rainwater for dissolved pollutants in
rain samples, [which] thus allowed us to analyze the filtered
particulate matter for fungal spores," he said.
In 2005, scientists collected spores in rainwater and looked at
them with a microscope. "This was a tedious process, and [it is]
very difficult to differentiate ASR from other rust spores,"
Szabo said. "They just can't confirm their identity."
Szabo and his colleagues last year [2005] received funding to do
a national survey to further develop the molecular assay and
monitor
124 sites across the Corn Belt.
"We covered all states south from North Dakota to Texas and east
to the Atlantic coast, except for the New England states," he
said. "We selected 124 sites to represent all of the soybean
growing areas in the central and eastern part of the U.S. All
the states contained more than one collection site. However,
since the network was established to monitor air pollution,
several key soybean states had only a few sites."
The NADP program took weekly samples, Szabo said. "Sites are
sampled weekly, every Tuesday morning," he said. "We have
samples from the mid-May through early November."
Rainwater samples were collected and then filtered by the NADP
staff, Szabo said. Filter papers with particular matter
containing the rust spores was dried and then tested for DNA of
ASR spores.
Unfortunately, there is not a good molecular method to test for
viability, and it is unlikely spores survived collection and
transport.
One important aspect of the project was developing a molecular
method to detect the ASR spores, Szabo said, so they modified a
real-time polymerase chain reaction assay developed by
scientists at Fort Detrick, Maryland.
Polymerase chain reaction is a method for amplifying DNA. This
is important, because a few spores do not contain enough DNA for
identification. But if you amplify the DNA by making many
copies, it is easier to confirm the identity with the necessary
degree of accuracy.
Szabo and his colleagues collected more than 3000 samples and so
far have analyzed 1600 samples and found 85 positives. So far,
the team has processed and reported on samples collected through
August 2005.
About 1400 samples remain to be processed and reported, and
processing the samples is tedious, Szabo said.
"It takes 4 people working full time to process a couple hundred
samples a week," he said.
The 1st spores were detected in May 2005 in North and South
Carolina and Tennessee, Szabo said.
The team's survey reports that in June 2005, spores were
detected in 11 states from Florida to Texas to Minnesota and
North Dakota, but skipping the central Corn Belt. In July 2005,
spores were detected in 13 states in the south, the Appalachian
mountain range and the northwestern Corn Belt. In August 2005,
spores were found in 17 states in the south, the Allegany
mountain range, the eastern Corn Belt and the northwestern Corn
Belt.
"The 85 positive findings were distributed throughout [the]
soybean growing area," Szabo said. "There were no positive finds
for Illinois, Iowa, Nebraska or Oklahoma. But there were
positive findings in Michigan, Minnesota, Missouri, North
Dakota, South Dakota and Wisconsin."
Scientists don't yet understand why ASR spores were found in the
northern states but not in these central Plains states, Szabo
said.
"This could be a result of the low number of rainwater
collection sites in these states or the track of rain storms
which transported the spores further north," he said. "This
needs further study."
Texas had several positives during summer, which was a surprise,
Szabo said, but Georgia had none.
Georgia was drier than normal, but Szabo said he did not
understand why they did not find any rainwater samples in the
state. One reason may be the weather patterns and where spores
are picked up by the storms.
The southern end of the Appalachian mountain range also had
several positives, he said, because of the way storms track
north northeast out of the gulf, hit mountain ranges and deposit
rain and spores.
"Interestingly, preliminary analysis indicates that there was no
clustering of positive finds associated with Hurricane Katrina
or Rita," he said. "We found no correlation between spore
deposition and tropical storm events in 2005."
ASR spores were found across most of the Midwest and northeast
throughout the summer, Szabo said. The spores are easily
transported via the atmosphere over long distances, but
scientists don't know whether the spores are viable. Once they
finish their sample processing, they will know whether spores
were found at one time or another in the entire soybean
producing state.
Szabo said he and his colleagues plan to repeat the survey again
in 2006.
[Byline: Daniel Davidson]
--
ProMED-mail
<promed@promedmail.org>
[5]
National Map Commentary (updated: 17 Feb 2006)
Date: 17 Feb 2006
From: ProMED-mail <promed@promedmail.org>
Source: Sbrusa.net [edited] <http://www.sbrusa.net/>
National Map Commentary (updated: 17 Feb 2006)
The only 2 known rust positive sites in Georgia in 2006, one in
Grady county and one in Thomas county, were removed/destroyed.
As a result, these counties have been turned back to green on
the observation map.
Please consult state commentary for more information.
Scouting for ASR continues on kudzu patches from Florida
northward through Georgia and Alabama, and westward to Texas.
The confirmed reports of kudzu in 2006 include Alabama with one
and Florida with 11 counties. Due to the recent cold
temperatures in northern to mid Florida, much of the kudzu has
died back. In one location just north of Ocala, Florida new
growth from this year [2006] had reached 3 to 4 feet in length,
but was dead due to the frost on 14 Feb 2006. Other sites
further south of there and east of Tampa also suffered from the
frost. In general, there was about 90 percent kill of leaves
from new growth in 2006 in the sites west of Tampa. There may
still be some green kudzu in southernmost Alabama and Georgia in
protected sites.
The possibilities of frost are not over in Florida, as the last
frost-free date for parts of northern Florida goes to 15 Mar
2006. In general, as temperatures warm in central Florida, the
kudzu is likely to leaf out very quickly, as most stems and buds
are green and ready to grow.
--
ProMED-mail
<promed@promedmail.org>
[6] Ohio to use
sentinel plots in 2006
Date: 17 Feb 2006
From: ProMED-mail <promed@promedmail.org>
Source: Stopsoybeanrust.com [edited]
<http://www.stopsoybeanrust.com/viewStory.asp?StoryID=687>
Ohio to maintain its 45 ASR sentinel plots in 2006
Sentinel plots, established throughout the country last year
[2005] as the 1st line of defense against ASR, will again be a
part of the plan to monitor the disease this growing season.
Anne Dorrance, an Ohio State University plant pathologist with
the Ohio Agricultural Research and Development Center and the
state's leading ASR expert, said that Ohio will maintain its 45
sentinel plots.
"The sentinel plots worked, and they worked very well, and we
got good participation from the counties. The Extension
educators did an outstanding job scouting the sentinel plots,"
said Dorrance, who also holds an Ohio State University Extension
appointment. "Because of the sentinel plots placed throughout
the South, we will know a month ahead of time if we are going to
be at risk from ASR during 2006."
According the USDA, sentinel plots have been established in more
than 30 states and Canada, stretching as far south as Florida,
as far north as Ontario, as far east as Delaware and as far west
as Washington.
A total of 138 counties throughout the United States tested
positive for ASR last year [2005]. The closest ASR got to Ohio
was Kentucky, where one rust pustule was found on kudzu in
November 2005, long after the soybean crop had been harvested.
This year, the extent of the disease's spread will hinge on how
well wintry weather in the South will hold the disease back.
"The big questions are how low will the freeze line go in the
South, and how soon will the inoculum build up this spring
[2006]," said Dorrance. "We've been having anything but a normal
winter this year, so anything can happen."
So far this year [2006], the USDA has reported positive ASR
finds on kudzu in Alabama, Georgia and Florida.
"Even if we get a lot of inoculum build-up this year [2006], an
unexpected epidemic in Ohio would be unlikely," said Dorrance.
"At just a 3 percent infection level in soybean fields across
the state, we would have to have 12 million spores hit every
acre in the state all at the same time. With 5 million acres,
that just doesn't compute, and we'd know that ASR was present
long before it ever reached that level because it would be
everywhere."
Nonetheless, researchers are keeping a close watch on the
disease's potential path north. ASR can enter Ohio through a
variety of routes:
south through Kentucky, from North Carolina over the Appalachian
mountains, or up the Mississippi River and along the Ohio River
through southern Indiana and western Kentucky.
"The network is in place. It's safe to say we've got all of that
covered," Dorrance said.
For the latest information on ASR, log on to the USDA's Soybean
Rust Information Site.
OARDC plant pathologist Dennis Mills will provide a ASR update
at the Conservation Tillage and Technology Conference 23-24 Feb
2006 at Ohio Northern University in Ada, Ohio. For more
information, go to <http://ctc.osu.edu>.
SOURCE: News release from the Communications and Technology unit
of Ohio State University's College of Food, Agricultural, and
Environmental Sciences.
--
ProMED-mail
<promed@promedmail.org>
One of the sites that had an April 2005 detection of the fungal
pathogen _Phakopsora pachyrhizi_, the cause of ASR, on kudzu
(_Pueraria lobata_, a.k.a. Japanese arrowroot) in Dade County
Florida was confirmed to be an infected site in 13 Feb 2006. A
2nd site in
2006 was found in Georgia in Thomas County on 13 Feb 2006, but
the kudzu at this and an earlier positive site in Georgia was
removed.
This means that Florida and Alabama are the only 2 states to
have known infection centers.
Taking these events into account, the confirmed reports of
infected kudzu in 2006 in mid February now include Alabama with
one and Florida with 11 counties. The role of kudzu in the
epidemiology of ASR is not clear in the southern states of the
USA, where frost can still (February) be a factor that could
kill plants, including those that have survived in protected
spots and which account for several of the finds to date.
Questions remain about ASR spore producing capacity on kudzu and
whether all biotypes of the plant are equal in levels of
defoliation and spore production when infected. The use of rain
collections, which can be monitored for spores of ASR by
molecular methods, has been demonstrated. 1600 samples collected
in 2005 were tested, and to date, 85 were positive for ASR. The
effectiveness of doing this as a method to monitor disease
potential remains to be confirmed, and has the obvious handicap
of only being useful where it has been raining, in contrast to
the collection of aerial spores. Neither method can predict the
viability of the spores detected. The use of sentinel plots will
again be a major tool for spotting early infections should they
occur in northern states like Ohio (none in 2005), or monitoring
when they occur in states to the south. Note the 1st report of
ASR in Mexico in the "see also" section.
Maps: <http://www.sbrusa.net>
Pictures: <http://www.dtnsoybeanrustcenter.com/index.cfm?show=65&mid=60&page=ALL>
Diagnosis cards (broadband best) <http://www.aphis.usda.gov/lpa/issues/sbr/SBR_IDcard_11-04.pdf>
Links:
<http://www.sbrusa.net>
National commentary, updates from states, maps, chronology.
<http://www.stopsoybeanrust.com/mc_home.asp>
Latest news, articles, maps and tracking information.
<http://www.dtnsoybeanrustcenter.com/index.cfm?show=10&mid=31>
Latest news, articles and other information.
<http://www.stopsoybeanrust.com/mc_resources.asp>
More links on ASR. - Mod.JAD]
[see also in the
archive:
Soybean rust - Mexico: 1st report 20060219.0546 Soybean rust,
Asian strain update 2006 20060214.0482 Soybean rust, Asian
strain - USA (GA) 20060208.0415 ProMED-Plant Disease Report:
July - December 2005 20060201.0331
2005
----
Soybean rust, Asian strain - USA: 2005 disease summary
20051228.3694 Soybean rust, Asian strain - USA (KY)(02):
confirmed 20051219.3640 Soybean rust, Asian strain - USA
(multistate) (10) 20051218.3628 Soybean rust, Asian strain - USA
(KY): 1st report 20051123.3404 Soybean rust, Asian strain - USA
(multistate)(09) 20051101.3187 Soybean rust, Asian strain, kudzu
control 20051006.2914 Soybean rust, Asian strain - USA (GA)(05)
20051005.2902 Soybean rust, Asian strain - USA (AL)(04)
20050917.2743 Soybean rust, Asian strain - USA (multistate)(08)
20050913.2711 Soybean rust, Asian strain - USA (multistate) (07)
20050909.2672 Soybean rust, Asian strain - USA (GA) (04)
20050905.2623 Soybean rust, Asian strain - USA (multistate)(04)
20050829.2556 Soybean rust, Asian strain - USA (GA)(03)
20050827.2531 Soybean rust, Asian strain - USA (AL)(03)
20050826.2528 Soybean rust, Asian strain - USA (AL)(02)
20050824.2496 Soybean rust, Asian strain - USA (SC)
20050818.2414 Soybean rust, Asian strain - USA (FL)(03)
20050815.2386 Soybean rust, Asian strain - USA (Multistate)(06)
20050808.2318 Soybean rust, Asian strain - USA (multistate)(05):
susp. 20050806.2291 Soybean rust - USA (multistate)(04)
20050806.2289 Asian soybean rust, Asian strain - USA
(multistate) 20050724.2133 Soybean rust, Asian strain - USA (AL)
20050715.2029 Soybean rust, Asian strain - USA (multistate)(03)
20050714.2005 Soybean rust, Asian strain - USA (multistate)(02):
Florida 20050708.1938 Soybean rust, Asian strain - USA
(multistate) 20050702.1868 Soybean rust, Asian strain - USA (LA)
20050624.1769 Soybean rust, Asian strain - USA (FL) (02)
20050620.1731 Soybean rust, Asian strain - USA (GA)
20050505.1245 Soybean rust, Asian strain - USA (GA)
20050429.1196 Soybean rust, Asian strain - USA (FL): 1st report
2005 20050309.0693]
